BUG #19548: Missing dependency between a graph edge and the related PK

The following bug has been logged on the website:

Bug reference: 19548
Logged by: Christophe Courtois
Email address: christophe(dot)courtois(at)dalibo(dot)com
PostgreSQL version: 19beta1
Operating system: Linux Debian 13
Description:

Hi,

A dependency between a graph and the PK of a relationship
seems to be missing.

In the following example, a PK on the edge table is compulsory,
but this PK can be cascade-dropped and the graph is unchanged.

The graph can be dropped later,
but it cannot be recreated :
ERROR: no key specified and no suitable primary key exists for definition
of element "family"

I imagine that a pg_restore will fail too.

Tested on 19~beta2-1~20260629.2015.g9cfd19bc10a.pgdg13+1 from
apt.postgresql.org
and 20devel freshly compiled.

Full example :

-- persons
CREATE TABLE persons (
id TEXT PRIMARY KEY,
nom TEXT,
sexe TEXT
);

CREATE TABLE family (
id TEXT PRIMARY KEY,
spouse1 TEXT REFERENCES persons(id),
spouse2 TEXT REFERENCES persons(id)
);

CREATE PROPERTY GRAPH wedding
VERTEX TABLES (
persons KEY (id) PROPERTIES ALL COLUMNS
)
EDGE TABLES (
family
SOURCE KEY (spouse1) REFERENCES persons (id)
DESTINATION KEY (spouse2) REFERENCES persons (id)
);

-- Drop the constraint
-- CASCADE does NOT get rid if the graph

ALTER TABLE family DROP CONSTRAINT family_pkey CASCADE ;

-- The graph is still there

\dG+

-- Recreation fails

DROP PROPERTY GRAPH wedding ;

CREATE PROPERTY GRAPH wedding
VERTEX TABLES (
persons KEY (id) PROPERTIES ALL COLUMNS
)
EDGE TABLES (
family
SOURCE KEY (spouse1) REFERENCES persons (id)
DESTINATION KEY (spouse2) REFERENCES persons (id)
);
ERROR: no key specified and no suitable primary key exists for definition
of element "family"
LINE 6: family